We propose to continue to develop novel methods of bone marrow culture with the objective of obtaining long-term proliferation of hematopoietic stem cells. Further, we plan to develop a clonogenic assay for human T lymphocytes. BIBLIOGRAPHIC REFERENCES: Cline, M.J., and Golde, D.W. Improved techniques for liquid culture of human and mouse bone marrow. Blood 47:369-379, 1976. Cline, M.J., Le Fevre, C., and Golde, D.W. Organ interactions in the regulation of hematopoiesis: In vitro interactions of bone, thymus, and spleen with bone marrow stem cells in normal, Sl/Sld and W/Wv mice. J. Cell. Physiol., in press, 1976.